A honeycomb structure is widely used for catalyst carriers and various filters. Recently, the honeycomb structure gets attention as a filter for trapping particulate matter exhausted from diesel engine (hereinafter referred to as DPF).
Such a honeycomb structure generally contains ceramics as a main component in many cases. Following method is generally taken for producing the honeycomb structure. After adding several kinds of additives to the ceramic raw material to form clay, the clay is extruded to form honeycomb formed body, then the formed body is dried and fired to obtain the honeycomb structure.
In the forming step and the drying step in such a producing method, deformation such as distortion and a twist of the formed body occurs. The honeycomb structure is divided into a plurality of honeycomb-structure segments in basic shapes of rectangular prisms and the segments are joined to and integrated with each other in some cases. In such cases, it is difficult to join the segments to each other when deformation such as distortion and twists occur in the respective segments.
As a method for inhibiting distortion and the like in drying, there is a method for drying a ceramic formed body having a honeycomb structure by using a drying jig having an upper jig and a lower jig equipped with pressure applying means, the applied pressure being preferably 0.4 to 0.6 MPa as disclosed in Japanese Patent Application Laid-open No. 2001-130973. There is a drying jig having two separate jigs formed in such a way that they enclose in a closely contacted state nearly the whole surface of sides parallel to a longitudinal direction of a ceramic formed body having a honeycomb structure as disclosed in Japanese Patent Application Laid-open No. 2001-19533. In these methods, though the distortion of the formed body can be inhibited, cells may be collapsed in some cases, which may result in cross sectional deformation of the formed body. In these methods, deformation in a forming step is not taken into consideration at all.